Expanded perlite and vermiculite particles have gained widespread popularity throughout the insulation industry. They exhibit a relatively good thermal resistance and are excellent fire retarders. Using the method of this invention, a higher thermal resistance than possessed by untreated perlite is achieved. It should be noted that untreated perlite has a thermal conductivity or "R" of 2.7 per inch. Using the unique method of this invention, the thermal resistance of a perlite containing insulation product is substantially increased in value.
Attempts have been made in the past to affix perlite and other particles to a substratum. One technique used was to premix the perlite and a binder and force the material through a plater type of machine and then through a spray gun. This method allows the mixture to harden prematurely, causes some particles to crush and lose particle size effectiveness, causes damage to the machine and has a very high loss ratio. Thus, up to 50% of the material has been wasted during application to a substratum in prior methods. Several other drawbacks were present in prior attempts to spray perlite upon a substratum. The amount of perlite and adhesive initially applied to a substratum and adhering thereto was often quite small. The application of the perlite aggregate and binder at a high velocity caused a high loss ratio of the applied material. The machines discharging the aggregate were designed for distribution of fibrous materials, and as the expanded aggregate was introduced within the machine, the machine has a tendency to crush a substantial portion of the particles. Perlite is a silicate and crushing of substantial portions of the perlite causes machine parts to "freeze" or adhere together due to silification, significantly shortening machine life.
Through extensive experimentation with prior art thermal insulation materials, machines, and spray nozzles, I have devised a new method of, and apparatus for, aggregate application to obtain the goals described herein.